An Analysis of Bubble Plumes in Unstratified Stagnant Water

Multiphase flows are ubiquitous in nature and engineering scenarios; examples include volcanic eruption, cloud formation, land reclamation and subsea oil well blowout. In these flows, one or more heterogeneous materials is/are transported by a turbulent carrier fluid (fluid, hereafter). Their interactions, as embodied in the fluid velocities, determine the final fate and transport of the heterogeneous materials. This dissertation investigates how turbulent kinetic energy (TKE) is created and injected into surrounding fluid by the rising bubbles in an air-water bubble plume. This analogue flow shares many similar fluid mechanical properties with oil well blowout plumes whose knowledge is important in disaster management. A comprehensive experimental program using acoustic Doppler velocimetry (ADV) and planar particle image velocimetry (PIV) has been carried out to measure fluid velocities inside the time-steady two-phase plume. Radial profiles of diffusion of TKE and turbulent dissipation rate are reported for the first time. From the fluid-phase TKE budget, it is found that approximately 55-60% of the total work done by bubbles is used to create turbulence in the carrier fluid. Results on the auto-spectral density function of velocity fluctuations reveal a -8/3 spectral slope instead of the classic Kolmogorov-Richardson value of -5/3, suggesting a fundamental difference in spectral energy transfer in this two-phase ow when compared to other simple boundary-layer shear flows, such as a singe-phase jet. This is supported by the subgrid scale (SGS) dissipation computed from the PIV data where it can be seen that the direction of energy cascade is always forward for a simple jet whereas it can be backward for the two-phase plume. On the other hand, a data interpolation method based on first-order autoregressive processes is developed to replace faulty or missing data in a time series of turbulent velocities. The method is shown to preserve both spectral slopes and energies of frequency components, for the range of slopes between -7/6 to -8/3. Further, the classical sample and hold interpolation is shown to be the limiting behavior of a first-order autoregressive process and therefore has theoretical underpinnings hitherto unknown in the literature

Prevalence of venous obstructions in (recurrent) venous thromboembolism:a case-control study

Background The role of venous obstructions as a risk factor for recurrent venous thromboembolism has never been evaluated. This study aimed to determine whether there is a difference in prevalence of venous obstructions between patients with and without recurrent venous thromboembolism. Furthermore, its influence on the development of post-thrombotic syndrome and patient-reported quality of life was assessed. Methods This matched nested case-control study included 32 patients with recurrent venous thromboembolism (26 recurrent deep-vein thrombosis and 6 pulmonary embolism) from an existing prospective cohort of deep-vein thrombosis patients and compared them to 24 age and sex matched deep-vein thrombosis patients without recurrent venous thromboembolism. All participants received standard post-thrombotic management and underwent an additional extensive duplex ultrasonography. Post-thrombotic syndrome was assessed by the Villalta-scale and quality of life was measured using the SF36v2 and VEINES-QOL/Sym-questionnaires. Results Venous obstruction was found in 6 patients (18.8%) with recurrent venous thromboembolism compared to 5 patients (20.8%) without recurrent venous thromboembolism (Odds ratio 0.88, 95%CI 0.23-3.30,p = 1.000). After a median follow-up of 60.0 months (IQR 41.3-103.5) the mean Villalta-score was 5.55 +/- 3.02 versus 5.26 +/- 2.63 (p = 0.909) and post-thrombotic syndrome developed in 20 (62.5%) versus 14 (58.3%) patients, respectively (Odds ratio 1.19, 95%CI 0.40-3.51,p = 0.752). If venous obstruction was present, it was mainly located in the common iliac vein (n = 7, 63.6%). In patients with an objectified venous obstruction the mean Villalta-score was 5.11 +/- 2.80 versus 5.49 +/- 2.87 in patients without venous obstruction (p = 0.639). Post-thrombotic syndrome developed in 6 (54.5%) versus 28 (62.2%) patients, respectively (Odds ratio 1.37, 95%CI 0.36-5.20,p = 0.736). No significant differences were seen regarding patient-reported quality of life between either groups. Conclusions In this exploratory case-control study patients with recurrent venous thromboembolism did not have a higher prevalence of venous obstruction compared to patients without recurrent venous thromboembolism. The presence of recurrent venous thromboembolism or venous obstruction had no impact on the development of post-thrombotic syndrome or the patient-reported quality of life

Ultrasound-accelerated catheter-directed thrombolysis versus anticoagulation for the prevention of post-thrombotic syndrome (CAVA): a single-blind, multicentre, randomised trial

Background: Early thrombus removal might prevent post-thrombotic syndrome by preserving venous function and restoring flow. Previous trials comparing additional catheter-directed thrombolysis to standard treatment showed conflicting outcomes. We aimed to assess the benefit of additional ultrasound-accelerated catheter-directed thrombolysis for the prevention of post-thrombotic syndrome compared with standard therapy in patients with iliofemoral deep-vein thrombosis. Methods: We did a multicentre, randomised, single-blind, allocation-concealed, parallel group, superiority trial in 15 hospitals in the Netherlands. Patients aged 18–85 years with a first-time acute iliofemoral deep-vein thrombosis and symptoms for no more than 14 days were randomly assigned (1:1) to either standard treatment with additional ultrasound-accelerated catheter-directed thrombolysis or standard treatment alone. Randomisation was done with a web-based automatic programme and a random varying block size (2–12), stratified by age and centre. Standard treatment included anticoagulant therapy, compression therapy (knee-high elastic compression stockings; 30–40 mmHg), and early ambulation. Additional ultrasound-accelerated catheter-directed thrombolysis was done with urokinase with a starting bolus of 250 000 international units (IU) in 10 mL NaCl followed by a continuous dose of 100 000 IU/h for a maximum of 96 h through the Ekos Endowave-system. Adjunctive percutaneous transluminal angioplasty, thrombosuction, or stenting was performed at the discretion of the physician who performed the intervention. The primary outcome was the proportion of patients with post-thrombotic syndrome at 12 months diagnosed according to the original Villalta criteria—a Villalta-score of at least 5 on two consecutive occasions at least 3 months apart or the occurrence of venous ulceration—and was assessed in a modified intention-to-treat population of all randomly assigned patients who passed screening and started treatment. The safety analysis was assessed in the same modified intention-to-treat population. This study is complete and is registered at ClinicalTrials.gov, NCT00970619. Findings: Between May 28, 2010, and Sept 18, 2017, 184 patients were randomly assigned to either additional ultrasound-accelerated catheter-directed thrombolysis (n=91) or standard treatment alone (n=93). Exclusion because of screening failure or early withdrawal of informed consent resulted in 77 patients in the intervention group and 75 in the standard treatment group starting allocated treatment. Median follow-up was 12·0 months (IQR 6·0–12·0). 12-month post-thrombotic syndrome occurred in 22 (29%) patients allocated to additional treatment versus 26 (35%) patients receiving standard treatment alone (odds ratio 0·75 [95% CI 0·38 to 1·50]; p=0·42). Major bleeding occurred in four (5%) patients in the intervention group, with associated neuropraxia or the peroneal nerve in one patient, and no events in the standard treatment group. No serious adverse events occurred. None of the four deaths (one [1%] in the intervention group vs three [4%] in the standard treatment group) were treatment related. Interpretation: This study showed that additional ultrasound-accelerated catheter-directed thrombolysis does not change the risk of post-thrombotic syndrome 1 year after acute iliofemoral deep-vein thrombosis compared with standard therapy alone. Although this trial is inconclusive, the outcome suggests the possibility of a moderate beneficial effect with additional ultrasound-accelerated catheter-directed thrombolysis. Further research is therefore warranted to better understand this outcome in the context of previous trials, preferably by combining the available evidence in an individual patient data meta-analysis. Funding: The Netherlands Organisation for Health Research and Development (ZonMw), Maastricht University Medical Centre, BTG-Interventional Medicine

The antibiotic doxycycline impairs cardiac mitochondrial and contractile function

Tetracycline antibiotics act by inhibiting bacterial protein translation. Given the bacterial ancestry of mitochondria, we tested the hypothesis that doxycycline—which belongs to the tetracycline class—reduces mitochondrial function, and results in cardiac contractile dysfunction in cultured H9C2 cardiomyoblasts, adult rat cardiomyocytes, in Drosophila and in mice. Ampicillin and carbenicillin were used as control antibiotics since these do not interfere with mitochondrial translation. In line with its specific inhibitory effect on mitochondrial translation, doxycycline caused a mitonuclear protein imbalance in doxycycline‐treated H9C2 cells, reduced maximal mitochondrial respiration, particularly with complex I substrates, and mitochondria appeared fragmented. Flux measurements using stable isotope tracers showed a shift away from OXPHOS towards glycolysis after doxycycline exposure. Cardiac contractility measurements in adult cardiomyocytes and Drosophila melanogaster hearts showed an increased diastolic calcium concentration, and a higher arrhythmicity index. Systolic and diastolic dysfunction were observed after exposure to doxycycline. Mice treated with doxycycline showed mitochondrial complex I dysfunction, reduced OXPHOS capacity and impaired diastolic function. Doxycycline exacerbated diastolic dysfunction and reduced ejection fraction in a diabetes mouse model vulnerable for metabolic derangements. We therefore conclude that doxycycline impairs mitochondrial function and causes cardiac dysfunction

The Antibiotic Doxycycline Impairs Cardiac Mitochondrial and Contractile Function

Tetracycline antibiotics act by inhibiting bacterial protein translation. Given the bacterial ancestry of mitochondria, we tested the hypothesis that doxycycline—which belongs to the tetracycline class—reduces mitochondrial function, and results in cardiac contractile dysfunction in cultured H9C2 cardiomyoblasts, adult rat cardiomyocytes, in Drosophila and in mice. Ampicillin and carbenicillin were used as control antibiotics since these do not interfere with mitochondrial translation. In line with its specific inhibitory effect on mitochondrial translation, doxycycline caused a mitonuclear protein imbalance in doxycycline-treated H9C2 cells, reduced maximal mitochondrial respiration, particularly with complex I substrates, and mitochondria appeared fragmented. Flux measurements using stable isotope tracers showed a shift away from OXPHOS towards glycolysis after doxycycline exposure. Cardiac contractility measurements in adult cardiomyocytes and Drosophila melanogaster hearts showed an increased diastolic calcium concentration, and a higher arrhythmicity index. Systolic and diastolic dysfunction were observed after exposure to doxycycline. Mice treated with doxycycline showed mitochondrial complex I dysfunction, reduced OXPHOS capacity and impaired diastolic function. Doxycycline exacerbated diastolic dysfunction and reduced ejection fraction in a diabetes mouse model vulnerable for metabolic derangements. We therefore conclude that doxycycline impairs mitochondrial function and causes cardiac dysfunction